Open Stack

Excerpts from Ben Nemec's message of 2018-04-30 16:16:35 -0500:
> Resending from an address that is subscribed to the list.  Apologies to 
> those of you who get this twice.
> 
> On 04/30/2018 10:06 AM, Doug Hellmann wrote:
> > It would be useful to have more input from PTLs on this issue, so I'm
> > CCing all of them to get their attention.
> > 
> > Excerpts from Doug Hellmann's message of 2018-04-25 16:54:46 -0400:
> >> It's time to talk about the next steps in our migration from python
> >> 2 to python 3.
> >>
> >> Up to this point we have mostly focused on reaching a state where
> >> we support both versions of the language. We are not quite there
> >> with all projects, as you can see by reviewing the test coverage
> >> status information at
> >> https://wiki.openstack.org/wiki/Python3#Python_3_Status_of_OpenStack_projects
> >>
> >> Still, we need to press on to the next phase of the migration, which
> >> I have been calling "Python 3 first". This is where we use python
> >> 3 as the default, for everything, and set up the exceptions we need
> >> for anything that still requires python 2.
> >>
> >> To reach that stage, we need to:
> >>
> >> 1. Change the documentation and release notes jobs to use python 3.
> >>     (The Oslo team recently completed this, and found that we did
> >>     need to make a few small code changes to get them to work.)
> >> 2. Change (or duplicate) all functional test jobs to run under
> >>     python 3.
> >> 3. Change the packaging jobs to use python 3.
> >> 4. Update devstack to use 3 by default and require setting a flag to
> >>     use 2. (This may trigger other job changes.)
> >>
> >> At that point, all of our deliverables will be produced using python
> >> 3, and we can be relatively confident that if we no longer had
> >> access to python 2 we could still continue operating. We could also
> >> start updating deployment tools to use either python 3 or 2, so
> >> that users could actually deploy using the python 3 versions of
> >> services.
> >>
> >> Somewhere in that time frame our third-party CI systems will need
> >> to ensure they have python 3 support as well.
> >>
> >> After the "Python 3 first" phase is completed we should release
> >> one series using the packages built with python 3. Perhaps Stein?
> >> Or is that too ambitious?
> >>
> >> Next, we will be ready to address the prerequisites for "Python 3
> >> only," which will allow us to drop Python 2 support.
> >>
> >> We need to wait to drop python 2 support as a community, rather
> >> than going one project at a time, to avoid doubling the work of
> >> downstream consumers such as distros and independent deployers. We
> >> don't want them to have to package all (or even a large number) of
> >> the dependencies of OpenStack twice because they have to install
> >> some services running under python 2 and others under 3. Ideally
> >> they would be able to upgrade all of the services on a node together
> >> as part of their transition to the new version, without ending up
> >> with a python 2 version of a dependency along side a python 3 version
> >> of the same package.
> >>
> >> The remaining items could be fixed earlier, but this is the point
> >> at which they would block us:
> >>
> >> 1. Fix oslo.service functional tests -- the Oslo team needs help
> >>     maintaining this library. Alternatively, we could move all
> >>     services to use cotyledon (https://pypi.org/project/cotyledon/).
> 
> For everyone's awareness, we discussed this in the Oslo meeting today 
> and our first step is to see how many, if any, services are actually 
> relying on the oslo.service functionality that doesn't work in Python 3 
> today.  From there we will come up with a plan for how to move forward.
> 
> https://bugs.launchpad.net/manila/+bug/1482633 is the original bug.
> 
> >>
> >> 2. Finish the unit test and functional test ports so that all of
> >>     our tests can run under python 3 (this implies that the services
> >>     all run under python 3, so there is no more porting to do).
> 
> And integration tests?  I know for the initial python 3 goal we said 
> just unit and functional, but it seems to me that we can't claim full 
> python 3 compatibility until we can run our tempest jobs against python 
> 3-based OpenStack.

Good point. The wiki page lists the integrated-gate-py35 job for
many projects, but not all will use that particular test job. I'm
not sure what other sort of integration jobs we do have, but I agree
we should have versions of them working for python 3.

> 
> >>
> >> Finally, after we have *all* tests running on python 3, we can
> >> safely drop python 2.
> >>
> >> We have previously discussed the end of the T cycle as the point
> >> at which we would have all of those tests running, and if that holds
> >> true we could reasonably drop python 2 during the beginning of the
> >> U cycle, in late 2019 and before the 2020 cut-off point when upstream
> >> python 2 support will be dropped.
> >>
> >> I need some info from the deployment tool teams to understand whether
> >> they would be ready to take the plunge during T or U and start
> >> deploying only the python 3 version. Are there other upgrade issues
> >> that need to be addressed to support moving from 2 to 3? Something
> >> that might be part of the platform(s), rather than OpenStack itself?
> 
> Alex can probably expand on this, but I know TripleO has some challenges 
> in this area.  Specifically the fact that CentOS 7 will only ever 
> support Python 2 and CentOS 8 is planned to only support Python 3. Since 
> CentOS 8 is not a thing yet and no release dates are announced they're 
> having to use Fedora for Python 3 testing, which isn't something that 
> will be supported long-term.  That makes things...complicated.
> 
> Some more details are in the PTG discussion wrap-up thread: 
> http://lists.openstack.org/pipermail/openstack-dev/2018-March/128481.html
> 
> That said, I believe the plan is to be testing on Python 3 by T, so I 
> guess that's ultimately the answer to your question.

Yes, that's more or less what I was looking for.

Doug

> 
> >>
> >> What else have I missed in these phases? Other jobs? Other blocking
> >> conditions?
> >>
> >> Doug
>